/Engine/Plugins/Runtime/MeshModelingToolset/Source/MeshModelingTools/Public/EditMeshPolygonsTool.h
Cut the current set of selected faces. Click twice in viewport to set cut line.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(CallInEditor, Category=FaceEdits, Meta=(DisplayName="CutFaces", DisplayPriority=5)) void CutFaces()